Thanks foggybottom, Jennifer Sullins (modelling as Ryonen for Hegre-Art) is very well-known, with distinctive facial features which make her instantly recognisable.
Of course, the question of a model's age is not so much how old she is now, but how old she was when the photograph was taken.
Your pictures from 'Olympia' were published on 26 March 2012, although the same Hegre-Art session yielded at least two further series which were published earlier and later than 'Olympia'.
In fact she posed for more than 50 Hegre-Art series, all published in 2011 - 2012, and I believe it is unlikely that any of them were actually photographed earlier than 2010, when she was 21 years old. Petter Hegre would certainly not have engaged her until she was at least 18.
She started modelling at the age of 19 and retired at 23.
If you have any more, I am sure we would all love to see her.
Meanwhile, here is a nice tribute by Swedish artist, Sandsh Konatski -